Geology 100


 


Assignment #1:


            The sedimentary rock and igneous rocks are subjected to pressures so intense or heat so high that they are completely changed (1997). They become metamorphic rocks, due to the process of metamorphism which does not melt the rocks, but instead transforms them into denser, more compact rocks. Metamorphic rock can become igneous rock when exposed to high temperature that is good enough to melt them forming magma, when volcano erupts, the lava flows and solidifies it become igneous rock. As rocks are eroded they are often broken into tiny pieces (relatively small sediments) coming from all types of rocks and are transported either through wind, ice and water (most important).  Once sediments are deposited, they become cemented together by minerals and chemicals or are held together by electrical attraction forming sedimentary rocks.


            Hardness scale was developed by a German mineralogist, ; to identify mineral properties. This is a good tool in differentiating hardness between different rocks and minerals if one is on rock collection or for the fun of identifying hard and soft. Color is one attractive property that is inherent to a rock or mineral that allows one to distinguish easily. However, some minerals have more than one color such as quartz having pink, blue, red, etc. Hence, streak was developed by geologist given to the colored residue left by scratching a mineral across an abrasive surface (. 2002). This in my opinion, experimental in nature wherein, a mineral such as hematite that can be red, brown or black, one thing that will distinguish it is that it will always leave a characteristic reddish brown streak.


            I could say volcanoes and mountain range are significant evidence of the tectonic plate theory. Volcanoes are usually situated either near the boundaries between tectonic plates or over geologically active hotspots (a location in the Earth’s surface that has experienced active volcanism for a long period of time). a specific example would be the Hawaiian Islands result from the slow movement of a tectonic plate across a “fixed” hot spot deep beneath the surface of the planet. On the other hand, a mountain range is a group of mountains bordered by lowlands or separated from other mountain ranges by passes or rivers. For an instance the Himalayas in Asia are the result of the Indian plate hitting the Asian plate, causing a ‘crumple zone’ near the line of impact.


 


Assignment # 2: 


A. Evolution through Time


1.         Animals evolve through various changes in the environment. Their way of survival primarily depends on the present environment they are in.  The following eras: Precambrian, Paleozoic, Mesozoic, and the Cenozoic are discussed further below with the specific characteristic that organisms dominate on the said era. Environmental changes such as mass extinction paved way to various forms that and now is predominantly called evolution.


            The Precambrian era includes the Proterozoic eon and the Archeaon eon, single celled organism like the blue – green algae and bacteria first appeared. Towards the end of the Archean eon the first multicellular, soft bodied animal began to emerge such as jellyfish and worms. Came forth the Cambrian period, where animals have had hard parts (hard shell) which marks the beginning of the Paleozoic era. The organisms that survived in this era had evolved including the first vertebrates. The late Paleozoic era was a time of great global changes that resulted to mass extinction. The impact of these mass extinction heralds the Mesozoic era, the age of the dinosaurs. Environmental change again triggered another round of world- wide mass extinction that killed the dinosaurs thus, came forth the Cenozoic time marked by intense tectonic changes these set the environment for mammals to dominate the land.


2.         Fossils literally mean ‘having dug up’ are mineralized or otherwise preserved remains or traces of animals and other organisms. The totality of fossils and their placement in fossil – containing rock formations and sedimentary layers is known as the fossil record.


            Fossilization is an atypical occurrence these are the mold and casts. The previous matter are formed when organisms die and are quickly buried by sediment. As the sediment turn to stone, the remains decay or dissolve and form a hollow cavity called molds. The latter is formed wherein bones and shell material may survive intact within sedimentary rock for millions of years that much of this material crystallizes or is replaced by minerals deposited from ground water preserving the original form is called cast.


3.         During the age of dinosaurs, the Mesozoic era. It has been discovered that there were dry and cool places that indicate that animals are warm blooded.  Life here was mire critical, from ancient to more modern forms. The Mesozoic era was ended with mass extinction through various explanations given by the scientist.


            Particular explanations are dust from extremely intense volcanic eruptions that changed the food chain dramatically or the large asteroid that struck the earth, cooling it, as smoke and dust blocked out sunlight. Whatever the cause, the environment is no longer suitable for living.


B.  Metamorphism


1.         Metamorphism can be defined as the solid state recrystallization of pre – existing rocks due to changes in heat and / or pressure and/ or introduction of fluids without melting.


            The two common types of metamorphism are contact metamorphism and regional metamorphism. In contact metamorphism it is directly related to the temperature, the imposition of magmas and taking place at or near the contact with the molten rock in a definite area this results to the formation of marbles. However, regional metamorphism involves both temperature and pressure on wide area coverage; a good example is the so – called amphibolite facies.           


2.         The changes in mineral assemblages are due to changes in the temperature and pressure conditions of metamorphism. Thus, the mineral assemblages that are observed must be an indication of the temperature and pressure environment that the rock was subjected to. This pressure and temperature environment is referred to as Metamorphic Facies; which is similar to the concept of sedimentary facies, a set of environmental conditions present during deposition.


            Metamorphic rock depend on the temperature they are formed such as the amphibole forms a temperature between 550 and 700 degrees centigrade, and at a pressure corresponding to a depth of at least 6 kilometers  that plots on the amphibole facies. Another mineral group that corresponds to a less intense metamorphic condition is the metamorphosed basalt that contains zeolites that could be plot in the zeolite facies.


C. Wind, Dust and Deserts


1.         Deserts are places that receive less than 25 cm (10 inches) of rain per year. They can be either cold or hot. Because of the lack of moisture in the air, heat quickly dissipates as the sun sets. In hot deserts, the temperatures can range from above 100 degrees Fahrenheit in the day to below 32 degrees Fahrenheit at night. Cold deserts generally receive more rainfall than do hot deserts. In cold deserts, temperatures in winter range between 32-39 degrees Fahrenheit with occasional snowfall. The deserts are typically located along the tropics of Cancer and Capricorn.


            There are several ways by which deserts are formed these are subtropical descent of equatorial air currents, rain shadow effects, great distance of land mass from the sea, cold coastal currents in warm latitudes and in the polar regions, the inability of cold air masses to hold too much moisture.


2.         Wind erodes the Earth’s surface by deflation, by the removal of loose, fine – grained particles, by the turbulent eddy action of the wind and by abrasion (the wearing down of surfaces of rock fragments (the wearing down of surfaces by the grinding action and sand blasting of wind borne particles). Wind – deposited sand bodies occurs as sand sheets, ripples, and dunes. Most commonly seen blowouts is known as desert pavement.


            Splash erosion is the detachment and airborne movement of snakk si\oil particles caused by the impacts of raindrops on soil. Sheet erosion is the result of heavy rain on bare soil where water flows as a sheet down any gradient, carrying soil particles. Surface runoff turbulence can often cause more erosion than the initial raindrop impact. The erosion is both downward, deepening the valley, and headward, extending the valley into the hillside.  


3.         Desertification is the degradation of land in arid, semi – arid and dry sub- humid areas resulting from various factors including climatic variations and human activities. Modern desertification often arises from the demands of increased populations that settle on the land in order to grow crops and graze animals.


            A number of solutions have been tried in order to reduce the rate of desertification and regain lost land. Leguminous plants, which extract nitrogen from the air and fix it in the soil, can be planted to restore fertility. Stones stacked around the base of trees collect morning dew and help retain soil moisture. Artificial grooves can be dug in the ground to retain rainfall and trap wind-blown seeds. In Iran, petroleum is being sprayed over semi-arid land with crops. This coats seedlings to prevent moisture loss and stop them being blown away (, 2006).


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